OPTION_REG datasheet(109/222 Pages) MICROCHIP

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DS22331A-page 109

MCP19111

19.0

I/O PORTS

In general, when a peripheral is enabled, that pin may

not be used as a general purpose I/O pin.

Each port has two registers for its operation. These

registers are:

• TRISx registers (data direction register)

• PORTGPx registers (reads the levels on the pins

of the device)

Some ports may have one or more of the following

additional registers. These registers are:

• ANSELx (analog select)

• WPUx (weak pull-up)

Ports with analog functions also have an ANSELx

power. A simplified model of a generic I/O port, without

the interfaces to other peripherals, is shown in

Figure 19-1.

FIGURE 19-1:

GENERIC I/O PORTGPX

OPERATION

EXAMPLE 19-1:

INITIALIZING PORTA

Write LATx

Data Register

I/O pin

Read PORTx

Write PORTx

TRISx

Read LATx

Data Bus

To peripherals

ANSELx

VDD

VSS

; This code example illustrates

; initializing the PORTGPA register. The

; other ports are initialized in the same

; manner.

BANKSEL PORTGPA;

CLRF

PORTGPA;Init PORTA

BANKSEL ANSELA;

CLRF

ANSELA;digital I/O

BANKSEL TRISGPA;

MOVLW

B'00011111';Set GPA<4:0> as

;inputs

MOVWF

TRISGPA;and set GPA<7:6> as

;outputs

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